This disclosure is directed to impact-modified thermoplastic compositions, articles formed therefrom, and their methods of manufacture, and in particular compatibilized thermoplastic compositions with advantageous properties such as improved impact strength, stable color, or desirable chemical resistance.
Polycarbonate homopolymers, polycarbonate copolymers, and polyetherimides are useful in a wide variety of applications at least in part because of their good balance of properties, such as moldability, heat resistance and impact properties, among others. Despite extensive research on these materials over the years, there still remains a need in the art for improved thermoplastic compositions that meet increasingly stringent industry standards.
For example, polyetherimides are known as outstanding high performance materials, having a high glass transition temperature (Tg), and high modulus and strength at elevated temperatures, good dimensional stability, as well as excellent chemical resistance. However, polyetherimides have a natural amber color with a yellowness index that can be greater than 50. This limits its colorability to dark or fairly light colors, but not to very light colors such as bright white colors. Further, the loading level of white pigment needed to achieve even fairly light color results in deterioration of mechanical properties especially poor notched-impact strength at room temperatures. Again, it is challenging to develop materials that retain the properties of polyetherimides, including chemical resistance, high flow, and high impact, but that can be manufactured as white materials without compromising these desirable properties.